I'm not an expert but as I understand it there is quite a lot of data available to allow flint tools to be dated from both the shapes used and the quality of the flint working. This data is not exact but has been built up over decades by looking at flint assemblages in a known datable context and using these to map how the shapes and quality varied over the various time periods.

Basically rougher, poorer flint tools are more modern as skills were lost as bronze and iron tools replaced stone working.

However would be risky to date based on one flint (as I think Phil has said on TT a number of times) - later in the program they had a handful of flint from one of the stone holes.

TT are normally pretty good an post-edit to correct anything they go wrong "live" so I'd guess there was more than one flint seen over the 3 days to make the statements made about the mound?

BTW - I loved the program TT back at it's best!

Mac